def my_half(list,item):
    low = 0
    high = len(list)-1

    while low <= high:
        mid = (low + high) // 2
        guess = list[mid]
        if guess == item:
            return mid
        if guess > item:
            high = mid - 1
        else:
                low =  mid + 1
    return None
my_list = [1,2,3,4,5,6,]

x = my_half(my_list,3)
y = my_half(my_list,1)
print(x)
print(y)
